Species

During the Majin Buu story arc, Trunks and his friend Son Goten are tasked with battling and defeating the evil Majin Buu, since there is no one else strong enough to challenge him. Though Trunks is not strong enough to fight Buu alone, he and Goten are taught the fusion dance technique, under the guidance of Piccolo, which allows the two to fuse into Gotenks, making them significantly stronger. They eventually fight Majin Buu and appear to be evenly matched, but soon run into trouble when the time limit on the fusion runs out. Luckily, Goten's older brother Son Gohan shows up just in time and easily overpowers Buu.

After blowing himself and disappearing for some time, Buu reappears and asks Trunks and Goten to fuse back into Gotenks, claiming that he wants to battle them. Trunks and Goten oblige Buu's request and perform the fusion dance, turning back into Gotenks. However, it turns out to be a trap as Gotenks, as well as Piccolo, are immediately engulfed by a large pink blob; a piece of Majin Buu that he had broken off earlier. Once Gotenks is completely covered by the blob, he is flung into Buu's body and absorbed.

Shortly afterwards, Goten's father Son Goku returns from the dead to fight alongside Gohan, but Gohan is also absorbed. Goku then fuses with Vegeta, becoming Vegito, and easily overpowers Buu. Vegito then allows himself to be absorbed by Buu so that he can rescue Trunks and the others and succeeds in doing so. After being released from Buu's body, Trunks dies when Buu blows up Eath, but is resurrected afterwards and aids in forming the Spirit Bomb that ultimately destroys Buu